Documenting Degrading Soil
A report tabled recently at Marlborough District Council’s Environment Committee has shown that the regions soils are at risk. Required under the Resource Management Act, the soil quality monitoring report determines the “life-supporting capacity of soil” and how current farming practice might impact on “the foreseeable needs of future generations”.
Marlborough District Council Environmental Scientist Matt Oliver, who wrote the report noted that soil quality was acceptable, but not improving, and that action should be taken to reduce the risks to the environment and production. The report notes that “degraded soils lose their productive capacity and become ineffective at filtering contaminants”.
Missing the Targets
The 2018 monitoring included 13 vineyard sites from a potential 158 subsites across the region. The samples were analysed for a series of chemical, physical and biological properties, which are used nationally and known to be robust indicators of soil quality. The results are assessed against a set of target ranges.
Oliver has expressed concern at the results noting continuing trends show soil degradation, with large numbers of samples failing targets, specifically in relation to phosphate and air-filled porosity, and lesser numbers failing anaerobically mineralised nitrogen, total carbon and nitrogen, C:N ratio and bulk density targets. Vineyard sites showed a significant effect in soil quality due to a decline in total carbon.
C-N The Real Costs
The overuse of agrichemical fertilisers plays a large role in the reduction in soil health, says Oliver. Leachates such as nitrogen and phosphate damage the ecological health of waterways by providing nutrients to unwanted algae and invasive plant species. Council wants to see a change in practice to reduce the risk of such pollution.
Aside from water quality issues, the long-term sustainability of the land and its ability to continue producing into the future is at stake.
The slow decline in soil health shown over 19 years of monitoring, Oliver believes, is a result of cultivation, when the soil loses organic matter. In viticulture, particularly, tractors cause compaction, which negatively affects soil porosity and water retention, increasing the need for irrigation, exacerbating the risk of leaching and leading to subsequent nutrient loss from the plants.
Increasing the organic matter applied to the soil improves all aspects of soil and mitigates the deterioration of grape production quality and our waterways.
Strong Interest in Fixing Underlying Issues
Viticulturalists in the region have clearly embraced a refreshed focus on soil health, as indicated by their presence at the Wholesale Landscapes-hosted Soil Health Field Day, last September. The event, attended by over 30 members of the viticulture industry, discussed sustainable solutions for improved vineyard management, providing growers with the most current information and tested solutions to specific challenges. It traversed all aspects of soil health, from initial analysis to remediation.
Following on from this, and seemingly indicative of an industry-wide change, Wholesale Landscapes’ sales of high-quality compost and organic matter have peaked this year, with volumes up 40%.
FishGro, one of Wholesale Landscapes’ specialist compost mixes, provides for those who require a BioGro-certified product, but increasingly, managers of conventional vineyards are moving towards a more a sustainable approach, applying additional organic matter to their soils and reaping the benefits of increased yield and higher quality fruit.